Summary of Work: For some elements, use of toenail levels as a surrogate measure of exposure may provide an estimate of exposure superior to that made on the basis of data from food frequency questionnaires, hair, blood levels, or other measures. Toenails reflect exposure over a longer period of time than do blood or urine measures, and are less likely to be influenced by contaminantion than hair. We hypothesize that toenail levels may provide a good measure of exposure for a group of elements (Ca, Mg, Fe, Zn, Cu, Mn, Se, Mo, Cr, Co, Hg, and Al), that has a purported link with chronic disease. Improved methods of assessing exposure to these elements will facilitate studies of their adverse or beneficial health effects. Repeated samples of whole-diet homogenates and toenails were collected over a one-year period from 77 subjects. The element content of diet and toenail specimens was determined by neutron activation analysis. Mid-range neutron activation analysis gave results for both food and diet for only 4 elements (Br, Ca, Cl, Mn), due to unanticipated difficulties in the laboratory. For example, in our population dietary copper levels were below the limit of detection for the assay, and dietary magnesium results were obscured by interference. Preliminary analyses suggest that nail manganese levels are inversely correlated with dietary intake (r-0.20). - Biological markers, Environmental exposure, Trace elements, Heavy metals, Nutrition assessment - Human Subjects